Strychnan and Secoangustilobine A Type Alkaloids from Alstonia spatulata. Revision of the C-20 Configuration of Scholaricine

A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A−E, 1−5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.

总计从Alstonia spatulata的叶子和茎皮提取物中分离出25种生物碱，其中五种为新型的strychnan型生物碱（alstolucines A−E，1−5），其余则为一种新型的secoangustilobine A型生物碱（alstolobine A，6）。通过核磁共振（NMR）和质谱（MS）分析确定了这些生物碱的结构，对于alstolucine B（2），还通过X射线衍射分析进行了确认。通过对scholaricine（13）的立体化学归属进行重新研究，利用核磁共振和X射线分析表明，C-20位的构型需要修正。生物碱1、2、6、7、9、10和13在长春新碱耐药的KB细胞中逆转了多药耐药性。